1. Field of the Invention
The present invention relates to a lighting apparatus, and in particular to a light-emitting diode (LED) lighting apparatus with fast changing focus which is applied to a variety of lighting device, such as an exhibition light.
2. Description of Related Art
Flashlights are widely used portable lighting apparatus in everyday life. In prior art, an adjustable flashlight can emit light beams with different intensity or different effective illumination distance by adjusting the position of light bulb with respect to reflective cone. However, lighting intensity and effective illumination distance of lighting apparatus are limited so that it cannot meet all requirements. When the light emitting diodes (LEDs) are used as light sources, the reflective cone and total internal reflection lens are adopted to focus light. However, the reflective cone and total internal reflection lens cannot achieve the function of adjusting the light distance. In addition, the reflective cone and total internal reflection lens restrict the adjusting distance so that the adjustable angle is small and the light beams cannot be adjusted with a wide angle.
China Patent Application No. CN3224922.5 published on Apr. 28, 2004 discloses an adjustable flashlight including a housing, a light bulb support connected with the housing, a light bulb positioned at the light bulb support, a reflective cone and a helmet. A switch is positioned at the housing of the adjustable flashlight, and the light bulb is electrically connected with the switch. A light emitting diode is positioned in vicinity of through hole of the reflective cone. Positive electrode and negative electrode of the LED are electrically connected with positive plate and negative plate respectively. The positive plate is in contact with positive electrode of power, and the negative plate is in contact with the housing of the adjustable flashlight. Effective illumination distance of the adjustable flashlight is adjusted by the position of the light bulb.
However, the adjustable flashlight described above utilizes the light bulb and the LED as light source, and the effective illumination distance is adjusted by different light source so that the structure of the adjustable flashlight is complicated and effective illumination distance is limited. When the effective illumination distance is adjusted from a small distance to approximately 30 meters, such as a night combat, a street battle, an upstairs-to-downstairs battle, or a floor-to-floor battle for soldiers and policemen that require a long distance focus, if the light is not focus the light is too weak to the soldiers and the policemen see anything. When the soldiers and the policemen execute a short distance battle, such as entering the floor, the stair, or the door, the light is focus on and the visional range is small so that a wide angle light source is required. In addition, the light flare produced by light beam reflected by reflective cone easily has the unbalance brightness symptom that it is bright in the center area and it is dark in the outer area. Therefore, a circular flare is formed.
Thus, there is a need for a lighting apparatus.